* {
    box-sizing: border-box;
    /* 统一盒模型计算方式 */
}

body,
div,
dl,
dt,
dd,
ul,
ol,
li,
pre,
form,
fieldset,
input,
textarea,
p,
blockquote,
th,
td {
    margin: 0;
    padding: 0;
}

ul,
ol {
    list-style: none;
    padding-left: 0;
    /* 清除列表缩进 */
}